1. Field of the Invention
The present invention relates to a DC/DC power conversion device for converting a DC voltage into a boosted or deboosted DC voltage.
2. Description of the Background Art
Japanese Publication of Patent Application H9-191638 discloses a DC/DC converter as a conventional DC/DC power conversion device which is comprised of inverter circuits including semiconductor switches connected to a voltage with a positive polarity (hereinafter, abbreviated to “positive voltage”) and semiconductor switches connected to a voltage with a negative polarity (hereinafter, abbreviated to “negative voltage”) and multiplier-rectifier circuits including a plurality of rectifiers connected in series and a plurality of capacitors connected in series. The inverter circuits generate alternating current (AC) voltages and the multiplier-rectifier circuits generate high DC voltages to a load.
Further, Japanese Publication of Patent Application 2006-262619 discloses a switched capacitor converter as a conventional DC/DC converter of another example which includes capacitors and inductors connected in series between a low voltage sided DC power supply and a high voltage sided DC power supply, and a plurality of semiconductor switching elements comprising cells for transferring energy between two power supplies. The n (n is an integer of 2 or more) cells are connected in parallel and driving signals for driving the semiconductor switching elements belonging to each cell are out of phase with each cell and the phase difference therebetween is 2π/n. This reduces ripple currents flowing through smoothing capacitors connected between respective input terminals and output terminals, thereby decreasing capacitances thereof.
Such conventional DC/DC power conversion devices perform a DC/DC power conversion using charge-discharge of capacitors and, according to the device disclosed in JP2006-262619, the plurality of cells are connected in parallel and the driving signals are out of phase and thus a structure of the device can be promoted to be small-sized by reducing the ripple currents flowing through the smoothing capacitors connected between the respective input terminals and the output terminals. However, the DC/DC power conversion device disclosed in JPH9-191638 is provided with the smoothing capacitors connected in parallel in the respective circuits such as the inverter circuits and the rectifier circuits. For this reason, although the DC/DC power conversion device is assumed as one cell to be comprised of a plurality of cells and to be out of phase with the cells connected in parallel like that disclosed in JP2006-262619, there is a problem that the ripple currents flowing through the smoothing capacitors connected in parallel in the respective circuits are not reduced.